This book offers us a brief but dense study of Bonhoeffer’s Habilitation thesis, Act and Being. DeJonge argues that it differs interestingly from Barth, that it follows a classic Lutheran line, and that it has more significance for understanding Bonhoeffer’s later work than has usually been allowed. Bonhoeffer classifies understandings of revelation as focused either on act or on being. Act, we are told, means discontinuous, contingent, and structurally open; being means continuous and structurally closed. Bonhoeffer engaged with Scheler and Heidegger, but he argues that all philosophy tends to orient itself around the self. His real interest was in Barth, the really exciting object in the theological firmament at this time. Barth committed himself to an act ontology very early on. It allowed him to emphasize the livingness of God, to get away from any notion of abstract deity, and it meant thinking of God as acting subject. In this way he could put clear blue water between himself and liberal Protestantism, which, in his view, had a fatal tendency to talk about faith, and thus the human being, rather than God. But, in his mischievous way, he also thought Lutheranism ran into a ‘Jesus Christ pit’. Feuerbach had simply spelled out where Lutheran theology leads, namely to a reversal of the divine–human relationship. For him the truth of the incarnation is that human beings are what we mean by ‘God’. To avoid that it was essential to make dogmatics Trinitarian. What this means for Christology is that it is possible to insist on the eternal difference between God and creature, and also to emphasize that the incarnation is the dynamic act of God on behalf of the whole threatened creation.